Postglacial vegetation history of southeastern Wyoming, U.S.A.

Abstract

Paleoenvironmental records from southeastern Wyoming have been compiled to show the development of forests in the Medicine Bow Mountains. The late-glacial period had little to no tree cover and a landscape dominated by alpine tundra, or alpine steppe-like conditions based on high abundances of Artemisia pollen. Initial conifer forest development began after 13,000 calibrated years Before Present (cal yr BP) with patchy, mixed fir-spruce-pine forests forming throughout the Medicine Bow Mountains. At lower tree line, pines in these forests contained limber pine based on pollen and macrofossil data, whereas at mid- and high elevations pine trees were most likely lodgepole pine. Forest densities increased after 9000 cal yr BP, with upper elevations dominated by Engelmann spruce and subalpine fir, while lower elevations were dominated by lodgepole pine that replaced limber pine. Modern forest conditions began to form after 5000 cal yr BP. The timing of past vegetation change in southeastern Wyoming appears consistent with those observed in the Greater Yellowstone region though pollen assemblages vary regionally.